main.py

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.scatter import Scatter
from kivy.core.window import Window
from kivy.uix.floatlayout import FloatLayout
from kivy.lang import Builder
Window.clearcolor = (1, 1, 1, 1)

Builder.load_string('''
<TextSquare>:        
           
    Label:
        markup: True 
        canvas.before:
            Color:
                rgb: 0,0,0,1
            Rectangle:
                pos: self.x - 10, self.y - 10
                size: self.texture_size[0]+20, self.texture_size[1]+20
        
            Color:
                rgb: 1,1,1,
            Rectangle:
                pos: 0,0
                size: self.texture_size
        font_size: 30  
        size: self.texture_size
        text: "[color=000000]TEST[/color]"
''')
                    
class TextSquare(Widget):
    pass
    
class ScatterTestApp(App):
    def build(self):
        f = FloatLayout()
        scatter = Scatter(do_rotation=False,do_scale=False)
        scatter.add_widget(TextSquare())
        f.add_widget(scatter)
        return f


if __name__ == '__main__':
    ScatterTestApp().run()